1. Field of the Invention
The present invention relates to a video game apparatus, its control method, a game program, and a computer-readable recording medium on which such a program is recorded. In particular, the invention relates to filtering processing on a scene in a virtual three-dimensional space.
2. Description of the Related Art
In 3D video games, a two-dimensional image is generated in real time based on objects etc. in a virtual three-dimensional space. A more realistic image can be generated by imparting visual effects to the generated two-dimensional image through various kinds of filtering processing. For example, filtering processing that blurs an image in accordance with the depth in a virtual three-dimensional space produces a perspective image.
Techniques of blurring an image in accordance with the depth in a virtual three-dimensional space in image processing on a three-dimensional computer image that is used in a video game are disclosed in Japanese Unexamined Patent Publication Nos. Hei. 10-222694 and Hei. 11-328437. For example, in the method disclosed in the publication No. Hei. 10-222694, influences of image data of each pixel on surrounding pixels are determined based on the difference between the Z value and the depth of field. And a calculation taking influences of surrounding pixels into consideration is performed for every pixel. In this calculation, the values of nine pixels that are the subject pixel itself and eight surrounding pixels are used. In this technique, the pixel value of every pixel is calculated under varied conditions that are determined for each pixel.